According to the brief statement, General Fan Changlong led a group of military commanders to the Spratly island group to visit troops and observe construction work.
The statement didn't say when and where Fan, a vice chairman of the Central Military Commission that controls the People's Liberation Army, visited.
The announcement comes after China issued an angry response to what it says are provocative plans announced yesterday that the US would send troops and planes to the Philippines for more frequent rotations and will increase joint sea and air patrols with Philippine forces in the South China Sea.
In reporting on Fan's visit, the ministry said China had completed work on five lighthouses, four of which are now operational, in the Spratlys, saying those were built to "provide a public service for the international community." Work on a weather station, ocean monitoring centre, oceanographic equipment and other facilities was also "proceeding smoothly," the report said.
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China claims virtually the entire South China Sea as its own territory and is topping the islands by piling sand and building airstrips and other infrastructure.
Late yesterday, the Defence Ministry said that Beijing would "resolutely defend" its sovereignty and maritime interests while accusing the Philippines and US of militarising the region and harbouring a "Cold War mentality" by strengthening their alliance.
The South China Sea dispute also featured in talks between Chinese Premier Li Keqiang and Malcolm Turnbull, the prime minister of close US ally Australia, which is trying to balance security needs with its economy's reliance on the Chinese market.